Single stage snowthrowers are so named because they utilize only one powered implement, the impeller, for picking up and throwing snow outwardly away from the snowthrower. In contrast, two stage snowthrowers utilize two separate powered means for handling snow.
Single stage snowthrowers generally include a housing which is open to the front and an impeller which is positioned in the housing. The impeller must be relatively flexible and wear resistant to endure contact with hard surfaces and clean such surfaces without harm. Most impellers are designed using a planar sheet of flexible material held into a desired shape by metal components.
Single stage snowthrowers in order to have best control of placement of thrown snow must gather snow from a relatively wide path toward a centrally located narrower discharge chute and accelerate the snow to obtain a good throwing distance. For best snowthrowing, single stage snowthrowers must dig into relatively hard snow without recirculating the snow and must have an impeller shaped to gather and accelerate the snow in usually less than one half rotation of the snow on the impeller.
Single stage snowthrowers are generally lighter and less expensive than two stage snowthrowers but they generally do not throw snow as well, as far, or as controlled as do the two stage snowthrowers. Problems typically include overfeeding of the snow by the ends of the impeller to the center of the impeller so that snow is delivered to the center faster than the impeller can remove the snow from the housing via a discharge chute. Snow splitting or throwing of snow forwardly of the snowthrower is a problem with single stage snowthrowers. Further, conventional impellers tend to push snow straight along a surface or push snow upwardly before the snow reaches the center of the impeller.